Donor challenge: Your generous donation will be matched 2-to-1 right now. Your $5 becomes $15! Dear Internet Archive Supporter,. I ask only. The Intel is a 5V only, ,bit Ultraviolet Erasable (Cerdip)/plastic production reside in a EPROM directly on a system’s memory bus. D K (32Kx8) uv EPROM in a 28 pin CERDIP package by Intel. Download Intel D datasheet: Status: NOS (New Old Stock), perfect condition.

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The programming process is not electrically reversible.

EPROM Technical Data

EPROMs had a limited but large number of erase cycles; the silicon dioxide around the gates would accumulate damage from each cycle, making the chip unreliable after several thousand cycles. While parts of the same size from different manufacturers are compatible in read mode, different manufacturers added different and sometimes multiple programming modes leading to subtle differences in the programming process.

In effect, the stored charge on the floating gate allows the threshold voltage of the transistor to be programmed. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits.

Because higher-density parts have little exposed oxide between the layers of interconnects and gate, ultraviolet erasing becomes less practical epprom very large memories. Views Read Edit View history.

Archived PDF from the original on For large volumes of parts thousands of pieces or moremask-programmed ROMs are the lowest cost devices to produce. Digital Design and Fabrication. This method of erasure allows complete testing and correction of a complex memory array before the package is finally sealed. The floating-gate electrode has no connections to other parts of the integrated circuit and is completely insulated by the surrounding layers of oxide.

Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. Magnetic tape Hard disk drive. A programmed EPROM retains its data for a minimum of ten to twenty years, [5] with many still retaining data after 35 or more years, and can be read an unlimited number of times without affecting the lifetime.


In other words, to erase your EPROM, you would first have to X-ray it and then put it in an oven at about degrees Celsius to anneal semiconductor alterations caused by the X-rays. Leaving the die of such a chip exposed to light can also change behavior in unexpected ways when moving from a windowed part used for development to a non-windowed part for production.

From Wikipedia, the free encyclopedia. International Trade Commission, ed. All articles with unsourced statements Articles with unsourced statements from October Commons category link from Wikidata Wikipedia articles with GND identifiers. Paper data storage Drum memory Magnetic-core memory Plated wire memory Core rope memory s Thin-film memory Disk pack Twistor memory — Bubble memory — Floppy disk EPROM programming is slow compared to other forms of memory.

Each bit of the word is a 1 or 0, depending on the storage transistor being switched on or off, conducting or non-conducting. Source and drain contacts are made to regions at the end of the channel. Even dust inside the package can prevent some cells from being erased.

The eproj window must be kept covered with an opaque label to prevent accidental erasure by the UV found in sunlight or camera flashes. The recommended erasure procedure is exposure to UV light at However, as this was not universal, programmer software also would allow manual setting of the manufacturer and device type of the chip to ensure proper programming.

A control gate electrode is deposited and further oxide covers it. An insulating eprrom of oxide is grown over the channel, then a conductive silicon or aluminum gate electrode is deposited, and a further thick layer of oxide is deposited over the gate electrode.


The first generation devices were fabricated with the p-MOS techology. Presence of a voltage on this gate creates a conductive channel in the transistor, switching it on.

Intel D27512-25 EPROM 27256 UV Erasable Prom

It was soon found that small-volume production was economical with EPROM parts, particularly when the advantage of rapid upgrades of firmware was considered. The process takes several minutes for UV lamps of 227256 sizes; sunlight would erase a chip in weeks, and indoor fluorescent lighting over several years.

To erase the data stored in the array of transistors, ultraviolet light is directed onto the die. Initially, it was thought that the EPROM would be too expensive for mass production use elrom that it would be confined to development only.

Development of the EPROM memory cell started with investigation of faulty integrated circuits where the gate connections of transistors had broken.

IC – 256 kbit EPROM (pulls)

When the high voltage is removed, the electrons are trapped on the electrode. Retrieved from ” https: This page was last edited on 8 Novemberat Stored charge on these isolated gates changed their properties. In other projects Wikimedia Commons. Cambridge University Press, p.

Non-volatile memory Integrated circuits Computer memory. Since the whole memory array is exposed, all the memory is erased at the same time. Shining ultraviolet light on any part of an unpackaged device causes a 72256 to flow from the floating gate back to the silicon substrate, thereby discharging the gate to its initial, uncharged condition photoelectric effect.